A molecular cytological approach to the structure and function of the synaptonemal complex is designed to address questions of how the DNA of eurkaryotic cells is organized into chromosomes and of how chromosomes pair, synapse, recombine, and segregate in meiosis. Recently, chromosome organization and behavior during meiotic prophase in the yeast Saccharomyces cerevisiae has been shown cytologically to be very similar to that in mammals, indicating evolutionary conservation in the underlying molecular mechanisms and allowing use of the sophisticated genetics and molecular genetics of yeast for examining the structural basis of the axial organization of chromosomes. The specific aims of this proposal are to identify and characterize the function of components of the synaptonemal complex in yeast, using a two-pronged approach. An immunocytological screen for antibodies that label the yeast synaptonemal complex will provide probes to be used to select clones from expression libraries. A screen for new classes of mutations will provide a complementary approach to identify genes that function in synaptonemal complex assembly, activates, and/or disassembly. The cytological, genetic, and molecular genetic analyses are expected to complement one another directly and to provide probes and ideas that will then be applied to questions of chromosome organization, behavior and transmission in mammals.